Unoctquadium
Unoctquadium, Uoq, is the temporary name for element 184. NUCLEAR What follows is based on a first-order, liquid-drop assessment of where the outer boundary of the nuclear world is. Assume cautious values for how many neutrons a nucleus with 184 protons can bind (high neutron dripline) and how few it can have before it fissions immediately regardless of how much the structure it can develop stabilizes it (low must-fission curve). Assume, too, that anything that lasts long enough so that protons and neutrons can be treated as particles rather than collections of quarks (is causal) might be a nucleus. Under these conditions, Uoq isotopes are theoretically possible between Uoq 460 and Uoq 805 (see "The Final Element", this wiki). Uoq 460 through Uoq 644 are expected to decay by beta emission if they don’t fission quickly. Above that value of A, the confident neutron dripline, drops may decay by neutron emission before they can fission. (Structural correction does not affect neutron emission.) Uoq 644 itself requires 1.5 MeV of structural correction energy to survive for the 10^-14 sec needed to bind an electron and so qualify as a nucleus. Uoq 739 and heavier don’t require any correction. Isotopes lighter than Uoq 485 need more than twice the correction energy needed to prevent fission in worst-case nuclei in the A = 480 region(1). In between, it is not usually possible to determine whether structural corrections will stabilize nuclear drops against fission. Neutron shell closures have been predicted at N = 406(2),(3),(4), 370(4), 318(5), and 308(1). The isotope Uoq 590 requires 3 MeV of structural correction, which means some isotopes in the Uoq 580 to Uoq 595 band are likely. Uoq 554 requires 6.5 MeV of structural correction, which means some isotopes in the band Uoq 544 to Uoq 559 are likely if the correction is strong. Long beta-decay half-lives in this band are expected, so decay by alpha emission is likely. Uoq 502 requires 19.5 MeV of correction energy and Uoq 492 requires 23.5 MeV, which implies that nuclides in these regions are unlikely. Between Uoq 485 and Uoq 689 some drops may be nuclei. Outside this band, isotopes of Uoq are nearly impossible. A proton shell closure is expected at Z = 184, but it is not expected to have a significant effect on which Uoq drops can be nuclei. ATOMIC Electron structure of Uoq has not been studied closely, but it is likely to differ significantly from the conventional orbitals found in lower-Z nuclei. While only the innermost electrons would be qualitatively different, other electrons are likely to be quantitatively different from those in lower-Z atoms. Uoq is also large enough that nuclear shape may have an effect on electron structure, which might cause different isotopes of Uoq to have different electronic structures. (That means it is no longer an element in the chemical sense.) Predictions of atomic or chemical properties of Uoq are risky. FORMATION Ions of this element may form when material from roughly 1 km depth is ejected from a disintegrating neutron star during a merger. It is probably impossible for lighter isotopes to form in this way. Fusion or multinucleon transfer reactions in the polar jets emanating from a neutron star or black hole might produce lighter isotopes, including those in the Uoq 580 to Uoq 595 and Uoq 544 to Uoq 559 bands. Quantities amount to a few atoms per star at best. REFERENCES 1. "Decay Modes and a Limit of Existence of Nuclei"; H. Koura; 4th Int. Conf. on the Chemistry and Physics of Transactinide Elements; Sept. 2011. 2. "Magic Numbers of Ultraheavy Nuclei"; V. Yu Denisov; Physics of Atomic Nuclei, v. 68, no. 7, pp 1133-1137; 2005. 3. “Search for Superheavy Elements Among Fossil Fission Tracks in Zircon”; J. Maly & D.R. Walz; Stanford Linear Accelerator Center publication SLAC-PUB-2554; July 1980. 4. “Single Particle Levels of Spherical Nuclei in the Superheavy and Extremely Superheavy Mass Region”; H. Koura and S. Chiba; Journal of the Physical Society of Japan; DOI 10.7566/JPSJ.82.014201; Jan. 2013. 5. “The Highest Limiting Z in the Extended Periodic Table”; Y.K. Gambhir, A. Bhagwat, and M. Gupta; Journal of Physics G: Nuclear and Particle Physics. 42 (12): 125105. DOI:10.1088/0954 3899/42/12/ 125105. (12-08-19)